AB0113 CHRONIC STIMULATION WITH SARS-COV-2 SPIKE PROTEIN DOES NOT TRIGGER AUTOIMMUNITY
Authors: M. Scherlinger, J. Sibilia, G. Tsokos, J. E. Gottenberg
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> Systemic autoimmunity is a complex and multifactorial process for which underlying mechanism are unclear. Several theories have been formulated to explain the development of autoimmunity, including excessive self-immunosurveillance, danger, and antigen discontinuity. The antigen discontinuity and the self-criticality theories presume that repetitive antigen exposure leads to a dysregulated immune response. Supporting these theories, Tsumiyama and Shiozawa have shown that repetitive immunization of BALB/c mice with ovalbumin induces auto-antibodies production and a glomerulonephritis with immune deposit resembling lupus nephritis [1]. These data prompted us to consider the potential impact of repetitive SARS-CoV-2 infection in the onset of autoimmune diseases in human. Indeed, since 2020, a large majority of the population has encountered SARS-CoV-2 antigens multiples times, either through vaccination or through infection/reinfection. Hence, we hypothesized that repetitive exposure to the SARS-CoV-2 spike antigen may induce autoimmunity in healthy individuals. <h3>Objectives</h3> Evaluate whether repetitive exposure to SARS-CoV-2 spike protein induces autoimmunity in mice. <h3>Methods</h3> We immunized intraperitoneally C57Bl/6 mice (n = 5/group) with recombinant SARS-CoV-2 spike protein (1µg per injection) or vehicle (phosphate buffered saline [PBS]); <b>Figure 1A</b>). The first injection was mixed with Alum as an adjuvant, and the other injections were diluted in PBS, administered intraperitoneally every 5 days, 16 times in total. Five days after the final injection, the mice were sacrificed to retrieve serum. We measured anti-spike and anti-dsDNA IgG using ELISA. The serum from 5 34-week-old C57Bl/6.lpr autoimmune mice were used as positive control. Briefly, 96-well plate were coated overnight with either spike protein (0.2µg/mL) or calf thymus DNA (0.1mg/mL; after precoating with poly-L-lysin 0.05mg/mL). After blocking with PBS-BSA, the diluted serum samples were incubated on the plate for 2 hours at room temperature. Plate-bound IgG were revealed using an alkaline phosphatase-conjugated anti-mouse IgG (1:5000). For anti-dsDNA IgG measurement, the serum of an autoimmune mice was used as a reference standard and the result expressed in unit per mL. <h3>Results</h3> After immunization, the phenotype of control and spike-immunized mice was clinically similar. All the immunized mice were exempt of proteinuria (<b>Figure 1B</b>). Only the mice which were injected with spike protein developed measurable amounts of anti-spike IgG as determined by ELISA, while those injected with PBS and the C57Bl/6.<i>lpr</i> mice did not (<b>Figure 1C</b>). None of the mice in the immunization group developed measurable anti-dsDNA IgG (<b>Figure 1D</b>). <h3>Conclusion</h3> In our study, the repetitive exposure of C57Bl/6 mice to the SARS-CoV-2 spike antigen did not lead to autoimmunity. Although these results are reassuring, large scale epidemiological studies are needed to evaluate the incidence of autoimmune diseases in individuals with multiple exposure to SARS-CoV-2 antigens. <h3>Reference</h3> [1]K. Tsumiyama, Y. Miyazaki, S. Shiozawa, Self-Organized Criticality Theory of Autoimmunity, PLOS ONE. 4 (2009) e8382. <h3>Acknowledgements:</h3> NIL. <h3>Disclosure of Interests</h3> Marc SCHERLINGER Speakers bureau: Amgen, Sandoz, Nordic Pharma, Jean Sibilia Speakers bureau: Roche, Chugai, Bristol-Myers Squibb, UCB, GSK, LFB, Actelion, Pfizer, MSD, Novartis, Amgen, Abbvie, Sandoz, Gilead, Lilly, Sanofi Genzyme, Janssen, Mylan, Galapagos, Sobi., Grant/research support from: Pfizer, BMS, Roche, MSD, George Tsokos: None declared, Jacques-Eric Gottenberg Speakers bureau: AbbVie, BMS, CSL Behring, Galapagos, Gilead, Lilly, Roche-Chugai, Pfizer, Sanofi, and UCB., Grant/research support from: BMS.